Yeah but Ã‚Â£50 is two months of the charge (Any discounts the OP may have will be on his phone account before anyone says anything) for BB L (4MB)
The reason it will have been restricted is they would have had to set up a new Direct Debit for the modem account, which probably didn't activate till AFTER the first bill was generated.
However the system (for some reason lost in the mists of time) doesn't e-mail to tell you that a bill is due UNLESS it is generated when the direct debit is already active, and that the bill is coming out via the D/D
Therefore the first bill notification the OP gets is for two months, one month of which is overdue (through no fault of the OP) and therefore it restricted the account
One of the many reasons it is going